<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        div {
            width: 200px;
            height: 100px;
            background-color: pink;
            transition: width 1s, height 1s;
            /* 如果要多个属性一起变化，写all就可以 */
            transition: all 0.5s;
        }

        div:hover {
            width: 400px;
            height: 200px;
            background-color: skyblue;
        }
    </style>
</head>

<body>
    <div class=""></div>
</body>

</html>